Professor Pip bounced out of his lab, his bushy tail swishing with excitement. A little girl named Lily was looking at a red maple leaf with a puzzled expression.

"Professor Pip," she asked, "Why is this leaf red? It was green all summer long!"

"Aha! That's a fantastic question, Lily," he chirped, tapping his crooked spectacles. "The secret is a special green food maker called chlorophyll."

He explained that plants use chlorophyll to turn sunlight into delicious sugary food. That's why leaves are usually so very green!

"Think of chlorophyll like a tiny little green chef," Professor Pip said with a grin. "It's working all day to cook for the tree."

The chlorophyll is so busy and so green that it hides all the other beautiful colors inside the leaf.

He held up a hand. "But what happens when the days get shorter?"

"And the sun doesn't shine as long and as warm?" he added, looking at the sky.

The trees know that winter is coming and it's time to rest. So they stop making that yummy sugary food.

This means they don't need the chlorophyll chefs anymore.

Slowly, the tree begins to pull all of the green chlorophyll back into its branches and trunk.

It's like the little green chefs are going on a long winter vacation.

As the green in the leaves fades away, something amazing happens. The colors that were always hiding underneath get to come out and play!

The yellows and oranges were there all along, patiently waiting for their turn to be seen.

And some leaves, like this one, get to show off a whole new color, like bright red or deep purple.

"But where does the red come from?" Lily asked, her eyes wide with wonder.

Professor Pip explained that some trees make special new sugars in the fall, which turn the leaves bright red.

It's like a final, beautiful burst of color before the leaves fall to the ground.

Lily looked at the red leaf with a new understanding and appreciation. "So the green is just sleeping?" she asked.

"Exactly!" Professor Pip cheered. "It will wake up again in the spring, ready to start its amazing work all over again."